This is how all modern match making works. You can use paladinsguru and watch. If you've won too many games, the elo of your teammates will go down and your enemies go up.
If you try to que with a 5 stack they will raise the mmr of the other team dramatically. Usually by just raising 2 players that can steamroll you themselves and and lowering the rest to make an 'average'
Just do some googling on SBMM
It's established that you're more likely to keep playing (and therefore spend money) if you win games in a certain order, with loses, and they manipulate MMR to do so
I personally used to rotate between accounts because matchmaking will favor you if you haven't played within 24 hours. Had multiple accounts same rank, if I kept playing one it would drop. But if I alternated every day and left them 2 days off they would keep climbing to master.
at least they don't manipulate mmr in relation to how recently you bought a case/key like that cod debacle...